This invention relates to a process for producing alkanolamines. Alkanolamines are valuable chemicals, which have applications as final or intermediate products in many industries such as pharmaceutical, chemical, petrochemical, etc.
Alkanolamines are routinely produced by reacting an alkylene oxide with an amine. The process is generally carried out in two distinct steps, wherein a reaction step is carried out in a reactor followed by a purification step, which is performed in a distillation column. There are two types of reaction of an alkylene oxide with an amine known in the prior art: an aqueous phase reaction and a non-aqueous phase reaction. The aqueous phase reaction, which is usually very fast, is carried out at low temperatures (usually less than 100° C.) by using water as a catalyst. The non-aqueous phase reaction is carried out at higher temperatures (usually greater than 100° C.) in the absence of water but in the presence of a product, which acts as a catalyst. A separate step to remove water from the product is required when water is used as a catalyst, making the overall process a three-step process.
There is a variety of processes commonly used for producing alkanolamines, wherein an alkylene oxide is reacted with primary or secondary amines. These processes comprise a step of reacting an alkylene oxide with an amine in a reactor followed by a step of distilling the reactor's effluent to recover and purify the desired alkanolamine. For example, U.S. Pat. No. 2,337,004 to Schwoegler describes a two-step non-aqueous phase process for producing alkanolamine. The two-step process involves (1) reacting an amine with an anhydrous alkylene oxide in a reactor and (2) recovering the product alkanolamine by distillation.
U.S. Pat. No. 3,131,132 to Moss et al. and U.S. Pat. No. 5,663,444 to Melder et al. describe two-step aqueous phase processes for producing alkanolamine. These two-step processes also involve (1) reacting an amine with an anhydrous alkylene oxide in a reactor and (2) recovering the product alkanolamine by distillation. See also U.S. Pat. No. 4,567,303 to Boettger et al.
Finally, European Patent EP 0919537 and Japanese Patent JP 09020733 describe two-step aqueous phase processes for producing an alkanolamine having a desired color. The disclosed two-step processes involve (1) reacting an amine with an alkylene oxide in an aqueous phase in a reactor and (2) recovering the product alkanolamine by distillation.
Althought we are aware of patents describing reactive distillation reactors and structures, we have not located art that describes production of alkanolamines from alkylene oxide and primary or secondary alkylamines by a reactive distillation process.
U.S. Pat. No. 6,075,168 to DiGuilio et al. describes a reactive distillation process for producing dialkanolamine from alkylene oxide and monoalkanolamine or a mixture of mono, di, and tri alkanolamines. This patent teaches the use of an alkanolamine feed stream rather than using ammonia or alkylamines. Even though a broad range of pressures is disclosed, the examples disclose a process conducted at a low pressure or vacuum to facilitate volatilization and stripping of alkanolamine in the reactive distillation column (see column 4, lines 24-27). The low pressure is used in this process because alkanolamines, in general, are less volatile than ammonia, primary amines, or alkylamines. The disclosed process does not teach the use of a catalyst such as water or a product alkanolamine to facilitate the reaction. In this process, the alkanolamine is used as a feedstock or a reactant.
The following U.S. Pat. Nos. 4,443,559; 5,057,468; 5,108,550; 5,130,102; 5,189,001; 5,221,441; 5,235,102; 5,262,012; 5,266,546; 5,291,989; 5,308,451; 5,348,710; 5,338,517; 5,431,890; 5,454,913; 5,449,501; 5,496,446; 5,504,258; 5,523,062; 5,593,548; 5,942,456; 5,601,797; 5,730,843; 5,779,993; 5,792,428; 5,847,249; 5,855,741; and 5,942,456; and PCT published applications WO 98/25696; WO 98/32510; and WO 00/26178 and South African Patent No. 950015 generally describe catalytic distillation apparatuses and methods, a liquid phase catalyst assembly for a chemical process tower, and/or an apparatus for conducting exothermic reactions. However, these patents do not disclose the production of alkanolamines from alkylene oxide and primary or secondary amines by reactive distillation process.
U.S. Pat. Nos. 4,504,687; 4,978,807; 5,196,612; 5,243,102; 5,248,837; 5,258,560; 5,321,163; 5,395,981; 5,504,258; 5,536,886; 5,744,645; and 6,008,416 describe a variety of processes for producing ethers and ketones using a reactive or a catalytic distillation. U.S. Pat. Nos. 4,935,577; 4,950,834; 5,043,506; 5,086,193; 5,476,978; and PCT published application WO 98/09929 describe a variety of processes for alkylation of aromatic compounds using reactive or catalytic distillation.
U.S. Pat. Nos. 5,463,134; 5,510,568; 5,597,476; 5,659,106; 5,863,419 and 5,679,241 describe catalytic distillation processes for removing sulfur and olefins from a variety of hydrocarbon streams. U.S. Pat. No. 5,336,841 to Adams and U.S. Pat. No. 5,516,955 to Gentry describe processes for processing and separating hydrocarbons by catalytic distillation. PCT published application WO 97/33953 describes a process for hydrogenating heavy unsaturates in an olefins plant by catalytic distillation. U.S. Pat. No. 6,084,141 to Mikitenko et al. describes a process for selective hydrogenation of light unsaturated hydrocarbons. These patents do not disclose the production of alkanolamines from alkylene oxide and primary or secondary amines by reactive distillation process.
U.S. Pat. No. 5,679,862 to Nemphos et al. discloses a catalytic distillation process for aminating aliphatic alkane derivatives in the presence of hydrogen and ammonia. U.S. Pat. No. 5,599,997 to Hearn et al. describes a catalytic distillation process for producing a cyclohexyl amine by hydrogenation of aniline.
Russian Patent RU 2162461 to Ryleev et al. discloses a process of producing ethanolamines by reacting ethylene oxide and anhydrous ammonia in the presence of monoethanolamine with in-process recycling of a liquid-phase ammonia. When an ammonia:ethylene oxide :monoethanolamine molar ratio reaches 20-30:1:1.5, the excess of the ammonia is removed from the reaction mixture by a distillation at 15-35 atm until the ammonia content is approximately 11 molar %. The rest of the ammonia is removed by an evaporation at 140-165° C. and 14-16 atm, followed by desorption at 160-165° C. and 2-4 atm, and absorption by monoethanolamine. The resulting absorbate, which contains approximately 6 molar % of ammonia, is returned into the initial reaction mixture. Monoethanolamine, diethanolamine and triethanolamine are recovered by known techniques. The removal of ammonia at 2-4 atm and its absorption with monoethanolamine enable in-process recycling of ammonia in a liquid phase, thus eliminating the need for a compression equipment or special cooling agents and reducing the ammonia content in final products to 0.1% or less.
International publication WO 2001053250 to Brun-Buisson et al. discloses a continuous multicolumn process for producing triethanolamine (TEA) comprising: (i) synthesizing the TEA by continuously bringing ammonia into contact with ethylene oxide under conditions allowing the formation of a reaction mixture comprising mono-, di- and triethanolamines; (ii) continuously separating the ammonia that has not reacted from the reaction mixture; and (iii) continuously separating the TEA from the mixture resulting from step (ii). The process is characterized in that a specific mixture of alkanolamines, comprising TEA and 0.5-50% of at least one secondary dialkanolamine (e.g., diethanolamine), is prepared or isolated from the mixture resulting from step (ii), and in that the TEA is separated and isolated with a degree of purity of ≧99.2% by a continuous distillation of the specific mixture of alkanolamines. The TEA produced is of high purity and has a high resistance to coloration.
An article by Brzozowski et al. (Technologia Chemiczna na Przelomie Wiekow (2000), 223-226 Publisher: Wydawnictwo Stalego Komitetu Kongresow Technologii Chemicznej, Gliwice) discloses that in a nucleophilic substitution reaction involving ammonia, H2O, alcohols or phenols (PhOH) can be used as catalysts. The manufacture of ethanolamines in a waterless environment under high pressure and at high temperature was examined. The reaction can be carried out successfully in the presence of traces of H2O present in the stream of reactants. When a 10:1 molar ratio of NH3 to ethylene oxide mixture was subjected to a reaction for several minutes at 10 mPa and 150° C., 100% conversion of ethylene oxide was achieved. At higher temperatures, the proportion of HOCH2CH2NH2 (MEA) in the products decreased and the proportion of (HOCH2CH2N)3 (TEA) increased. The product obtained at 100° C. contained more than 70% MEA and 5% TEA, while at 200° C. it contained 17% MEA, 17% (HOCH2CH2)2NH (DEA) and 63% TEA. A high excess of NH3 restricts side reactions of ethylene oxide and also increases the yield of MEA. The product obtained at a high NH3/ethylene oxide ratio (50-100:1) and a pressure of 15 MPa contained more than 90% MEA.
International publication WO 2000032553 to Ruider et al. discloses producing a crude triethanolamine by a liquid-phase reaction of aqueous ammonia with ethylene oxide under pressure and at an increased temperature, followed by a purification including the steps of: (1) separation of excess ammonia, water, and monoethanolamine from the reaction product, (2) ethoxylation of the separated products at 110-180° with an additional amount of ethylene oxide, and (3) vacuum distillation of the reaction product in the presence of phosphorous acid or hypophosphorous acid.
U.S. Pat. No. 5,663,444 to Melder et al discloses a process for making a color-stable dialkylaminoethanol by reacting ethylene oxide with a dialkylamine in the presence of from 2.5 to 50% by weight of water, based on the reaction mixture, at a temperature of from 95° to 170° C. and separating off the water and high-boiling constituents by distillation under a reduced pressure and at a temperature of from 40° to 90° C. at the bottom of the column.
Accordingly, it is desired to provide a process for producing alkanolamines by reacting an amine with alkylene oxide in the presence or absence of a catalyst in a reactive distillation apparatus.
All references cited herein are incorporated herein by reference in their entireties.